My present invention relates to a cannulation device and method and, more particularly, to a device which permits the introduction of a cannula into tissue of a patient, especially cardiac tissue and most specifically for ventricular cannulation as may be required for the installation of ventricular-assist devices which augment cardiac blood circulation.
Cardiac-assist devices can support circulation in cases of severe heart failure. Cardiac-assist devices, also referred to as ventricular-assist devices (VAD) draw blood from the left ventricle and eject it into the aorta. The blood is withdrawn through a tube or cannula introduced into the left ventricle, is displaced by a pump and is ejected through a tube which is inserted into the aorta.
The insertion of the tube into, for example, the ventricle through the cardiac tissue is referred to as ventricular cannulation and it is such introduction of the cannula that is the concern of this invention.
It should be noted that the implantation of a ventricular-assist device can be quite costly because the surgical procedure also requires intensive care required over a period of, say, twenty days. The high cost, long recovery time and related factors reduce the utility of the procedure for many patients. The assist device itself can be quite expensive in addition.
In addition to the high cost, conventional techniques involve major intervention and a traumatic procedure at lesat in part because of the need to connect the patient to a heart/lung machine. The latter technique is widely used but prolongs the duration of the surgery and increases the recovery time and the complexity of the equipment required for surgery. This major intervention increases the mortality and morbidity.
Conventional techniques for ventricular cannulation have involved piercing the cavity wall with a sharp tube over which the cannula can be fitted. Alternatively, a piece of tissue may be cut out of the ventricle with a coring knife. Both techniques require supporting the heart muscle which is pierced by the tool against the axial force applied against to the ventricle wall and cannot easily be accomplished while the heart is beating and full of blood.
The bleeding from the site can be extensive and can prevent the surgeon from seeing the action at the cardiac muscle wall. To assist having to handle the bleeding heart, the cardiac/pulmonary bypass approach has been used.
It is, therefore, the principal object of the present invention to provide an improved device for beating-heart cannulation, especially ventricular cannulation, that is simple to operate, inexpensive and eliminates the need to connect the patient to a heart/lung bypass circulation and thereby obviates the drawbacks described.
Another object is to provide an improved cannulation device which simplifies the surgical procedures involved, especially in cannulation for ventricular-assist devices, reduces complications in such surgical procedures and minimizes morbidity, mortality and cost.
It is also an object of this invention to provide an improved cannulation method whereby disadvantages of earlier cannulation systems are obviated.
I have found that the disadvantages of earlier systems with respect to the introduction of a cannula into tissue and especially the ventricular cannulation can be eliminated by eliminating the axial forces which are applied by the cannulation device implementation to the tissue while guiding the cannula into place, and, therefore, by spreading an incision in the tissue purely radially for this purpose. The term xe2x80x9ccannulation devicexe2x80x9d when broadly used in this description and the appended claims can include the surgical tools, therapeutic devices (balloons), diagnostic sensors, optical devices and any equipment for automating and/or monitoring the procedures described.
According to the invention, the procedure involves inserting into an incision in the tissue a narrow array of members which are then pressed outwardly without applying an axial component of force to the tissue, thereby spreading the incision and forming a circular opening while guiding within that array of members a cannula into the incision. Upon retraction of the members, therefore, the cannula is seized by the edges of the opening or incision as they naturally elastically contract around the cannula. The device can be anchored to the tissue by subsequent suturing to prevent it from sliding in or out.
More particularly, the cannulation device for the purposes described can comprise
a handle;
a plurality of pins in a circular array projecting from an end of the handle;
an actuator on the handle operatively connected with the pins for spreading the array from a narrow configuration in which the pins are insertable through an incision in tissue in which cannulation is to be effected into a wide position in which the tissue is radially and elastically spread at the incision; and
a cannula in the handle insertable through the array in the wide position for anchoring in the tissue by contraction of the tissue around the incision.
According to a feature of the invention the pins are formed as generally linear shanks on respective wire springs, each of the wire springs having a pivot portion parallel to the respective shank but offset laterally therefrom and a connecting portion between the respective shank and the respective pivot portion, the actuator including a sleeve provided with formations engaging the wire springs and rotating the connecting portions about axes of the pivot portions to radially displace the shanks between the positions.
The pivot portions are fixed on the handle whereby each of the wire springs is twisted about the respective axis by the respective formation, thereby torsionally stressing the respective wire spring, the shanks returning toward the narrow position by spring force resulting from the torsional stressing of the wire springs upon release of the actuator.
The actuator can have a lever projecting laterally form the handle and enabling rotation of the sleeve by a hand of a user holding that handle. The handle itself can be hollow and provided with a cut-out through which the cannula can be pressed through the array of pins into the opening by a finger of the user.
A cover can be fitted over the sleeve and the pivot portions of the wire spring at the end of the handle and can have an opening through which the shanks can project. The cannula, in turn, can have a tapered end adapted to lie in a body organ and an opposite end which can be connected to, for example, the intake side of the ventricular assist device.
It has been found to be advantageous to provide the formations as projections on an end of the sleeve. The array should include at least eight pins or shanks and the sleeve can project from an end of the handle and can have a cylindrical extension received in the handle. The sleeve and the handle can be connected by a rib-and-groove connection for axially fixing the sleeve to the handle.
The cannulation method can comprise the steps of:
(a) forming an incision in tissue into which a cannula is to be introduced;
(b) inserting into the incision a narrow array of pins;
(c) spreading the pins into a wide array to thereby radially expand the incision elastically and form an opening without axially stressing the tissue;
(d) inserting a cannula into the opening within the wide array of pins thereby plugging the opening; and
(e) withdrawing the pins from the tissue and leaving the cannula in the opening to eliminate bleeding or spilling of visceral fluids whereby the cannula is particularly retained in the tissue by elastic contraction of the tissue around the cannula.
The tissue is usually a ventricle wall and the cannula is inserted into a ventricle of the patient. The cannula is pushed into the opening simultaneously with the widening thereof by the pin. The cannula can thus be inserted into a beating heart without removal of the tissue from the ventricle wall.
With the system of the invention, once the incision is made, the only forces applied to the cavity wall are radial forces which spread the orifice to the diameter required by the cannula and no forces are exerted in the axial or inward direction. During the axial movement of the cannula, it is guided in a track formed by the shanks of the pins. The synchronous radial opening of the orifice and inward movement of the cannula seals the opening in the wall. The synchronous action of spreading the orifice and inserting the cannula can easily be accomplished by the single hand of a surgeon, but may be synchronized by a computer-controlled system operating respective actuators for spreading the opening and inserting the cannula. The pins preferably are of circular or semicircular cross section but can have other shapes as well. The shapes of the springs can also be varied and the shanks can be rigid or flexible.